(a) Field of the Invention
The present invention relates to a dot printer which has been improved to change the number of dots printed.
(b) Prior Art
FIG. 2 is a block diagram showing an example of the electric arrangement of the dot printer. A character font 2, a firmwear program 3 and the like are stored in a system cartridge 1 and character data is read out of the character font 2 one after another, responsive to signal applied from a central processing unit 4. These character data are applied to a printer head control unit 5, which controls a head driver 6 according to these character data to appropriately drive pins of a printer head 7. Line feed and head movement control signals are read out of the firmwear program 3 and applied to line feed and head movement control circuits 8 and 9, respectively, to appropriately control line feed and head movement step motors 10 and 11. The printer head 7, the head moving step motor 11 and the line feed motor 10 are thus appropriately controlled to carry out printing.
The printer head 7 has 9, 18 or 24 pins and the character data and the like become different, depending upon the number of pins of the printer head 7. The character font 2 and the firmwear program which correspond to the number of pins of the printer head 7 are stored in the system cartridge 1.
When the number of pins of the printer head 7 is increased to increase the number of dots which form a character, complicated configurations which represent Chinese characters, for example, can be clearly drawn, but the amount of data to be stored in the character font 2 becomes large accordingly and a large storage capacity is needed, thereby making the cost high. Alphabets and figures can be sufficiently discriminated one another even when they are printed by a small number of dots, and the number of pins of the printer head 7 can be thus decreased together with the amount of data to be stored in the character font 3, thereby making the cost low.
The printer head 7 and the system cartridge 1 were incorporated in to the printer in the manufacturing process in the case of the conventional dot printers, thereby making it difficult for the user to exchange them with new ones. Therefore, these dot printers which have a large number of dots were used to print Chinese characters and the like, while those dot printers which have a small number of dots were used to print alphabets and figures. The conventional dot printer were thus used depending upon what they were used for.